What legal law are you referring to? In IL all you have to do is licenses the truck for the gross weight you want to pull if you are commercial. My sons 3/4 Ram truck is licenses with D plate that has a gross weight of 30,000 lbs. This is to allow him to pull his car trailer with any vehicle on the trailer. DOT only looks at tire carrying ability and the license plate load registration of commercial vehicles.

FYI... a D plate in Illinois is only good for up to 12,000 lbs. Truck plate only accounts for the weight on the truck axles only. If, some how, your son has 30,000 lbs on the axles of a 3/4 ton he would need a K plate (28001-32000).

In Illinois, the flat weight plates should be bases on the GVWR Of the truck. He has D plates, as that 3/4 ton should have a GVWR of 9000 lbs, which fits nicely in the 8,001 to 12,000 lb range for a D plate.

If your son is legally (by plates) at 30k gross, then he would also need a TK plate on that trailer...

That's interesting; I guess than all of the aftermarket companies should close their doors. Since it is now illegal to alter the suspension with suspension lifts, or any other aftermarket components such as tires, wheels, CAI, tuners, bumpers, clutches, LED lighting attachments, air bags for improve ride characteristics and any other item that is sold for cars and trucks. Since most of these components do alter the manufacture functional specification and could change the weight placard that is attached to the B-pillar of the door frame.

You are correct, if you are in a wreck and end up in court a percentage of the fault can be place on after market products such as a lifted truck or large than normal tires. Say a lift truck with quick movement and rolls over and hurt someone you don't think if they are sued the fact the truck was lifted wouldn't be a percentage of cause of the truck rolling over and a percentage of the blame on the aftermarket products.

I have a 2013 XLR Viper and pull it with a 2012 Ram 3500 SRW that has been "decluttered" and chipped and really enjoy it. I do not see the reason for going the "dually" route. Don't care for the looks of them either.....